Real numbers in Intkey

Eric Zurcher Eric.Zurcher at CSIRO.AU
Thu Sep 2 06:43:16 CEST 2004


The proposal you described earlier sounds interesting in that it 
apparently attempts to allow for different levels of measurement 
precision by the key designer vs. the key user. I can see the value of 
that: the designer might have encoded a range of (for example) 3.35-3.85 
mm for a taxon; but a user attempting to identify a specimen from the 
large end of the range, yet able to measure only to the nearest 0.5 mm, 
might enter a value of "4", which would falsely exclude the taxon.

But the problem I see with this is: how can you reliably infer this 
precision? In my hypothetical example, the key user can measure to the 
nearest 0.5 mm. If she enters a value of, say, "4.5", how can Lucid 
"know" that this reflects a range of 4.25-4.75, rather than a range of 
4.45-4.55? There is also a problem with non-fractional values: Does 
"200" infer a range of 150-250, 195-205, or 199.5-200.5?

I don't see any reliable way get around this problem aside from 
burdening the user with the need to indicate the estimated error 
associated with their measurements.

Can you elaborate on how Lucid will deal with this?

Eric Zurcher
CSIRO Livestock Industries
Canberra, Australia
Eric.Zurcher at

More information about the delta-l mailing list